IRS Publication 936: Mortgage Interest Guide – IRS Publication 936 is the official IRS guide explaining how U.S. taxpayers can deduct home mortgage interest on their federal tax returns. For the 2025 tax year, this publication provides clear rules on qualifying for the deduction, calculating the allowable amount, and reporting it correctly on Schedule A (Form 1040). Whether you’re a first-time homeowner or refinancing an existing mortgage, understanding Publication 936 can help maximize your tax savings while staying compliant with current IRS rules.
This SEO-optimized guide breaks down everything from Publication 936 (2025) in plain language for American homeowners. All information is drawn directly from the latest IRS resources as of 2026.
What Is IRS Publication 936?
IRS Publication 936, titled Home Mortgage Interest Deduction, is the authoritative source for rules on deducting interest paid on mortgages, home equity loans, and related financing. It applies to individuals filing Form 1040 or 1040-SR who itemize deductions on Schedule A.
Published for use in preparing 2025 returns, the guide covers:
- What counts as deductible home mortgage interest
- Limits based on when you took out the loan
- Special rules for points (prepaid interest)
- Home equity debt restrictions
- Worksheets to calculate your exact deduction
You can download the full PDF for free at IRS.gov/publications/p936 or IRS.gov/pub/irs-pdf/p936.pdf.
Who Can Claim the Home Mortgage Interest Deduction?
To qualify for the deduction under Publication 936, you must meet these basic requirements:
- You file Form 1040 or 1040-SR and itemize deductions on Schedule A (the standard deduction is usually higher for most filers, so run the numbers).
- You paid interest on a secured debt (mortgage, deed of trust, etc.) on a qualified home in which you have an ownership interest.
- Both you and the lender intended the loan to be repaid.
The deduction is available for your main home (where you live most of the time) and one second home (such as a vacation property). A qualified home includes houses, condominiums, cooperatives, mobile homes, house trailers, or boats with sleeping, cooking, and toilet facilities.
Important note: Mortgage insurance premiums are no longer deductible for 2025 returns—the itemized deduction for them has expired.
Key Requirements: Secured Debt and Qualified Home
Publication 936 defines two critical terms:
- Secured debt: The loan must be recorded under state law with your home as collateral. A general lien or unsecured personal loan does not qualify.
- Qualified home: Your main home or a second home you designate for the year. If you rent out the second home, it must meet personal-use tests (used by you for more than 14 days or more than 10% of rental days).
Special cases include homes under construction (up to 24 months), destroyed homes (if you plan to rebuild), cooperatives (your share of the building’s mortgage interest), and time-shares that meet use requirements.
Mortgage Interest Deduction Limits for 2025
The biggest change from pre-2018 rules remains in effect. Publication 936 sets these debt limits:
| Loan Date | Maximum Deductible Debt | Married Filing Separately |
|---|---|---|
| On or before Oct. 13, 1987 (grandfathered) | No limit | No limit |
| Oct. 14, 1987 – Dec. 15, 2017 (home acquisition) | $1 million combined | $500,000 |
| After Dec. 15, 2017 (home acquisition) | $750,000 combined | $375,000 |
These limits apply to the combined total of all mortgages on your main home and second home. Higher pre-2018 limits apply only to debt actually incurred before December 16, 2017 (with a narrow binding-contract exception for early 2018 closings).
If your total mortgage debt stays under these limits and meets the use requirements, your entire home mortgage interest is usually fully deductible.
Grandfathered Debt vs. Home Acquisition Debt
Publication 936 uses two important categories:
- Grandfathered debt: Mortgages taken out on or before October 13, 1987.
- Home acquisition debt: Mortgages after that date used to buy, build, or substantially improve the qualified home that secures the loan.
Refinanced debt qualifies only up to the old balance. Home equity loans or HELOCs count as acquisition debt only if the proceeds were used to buy, build, or substantially improve the home securing the loan.
Rules for Home Equity Loans and HELOCs in 2025
This is one of the most common questions Publication 936 addresses. For tax years after 2017:
- Interest on home equity loans or lines of credit is deductible only if you used the money to buy, build, or substantially improve your main or second home.
- Using the funds for debt consolidation, vacations, or other personal expenses makes the interest nondeductible personal interest.
Pre-2018 rules were more generous (interest was deductible regardless of use), but those no longer apply.
Deducting Points (Prepaid Interest)
Points are upfront charges (like loan origination fees) paid to obtain a mortgage. Publication 936 explains two ways to deduct them:
- Fully deductible in the year paid if they meet strict tests (secured by your main home, established business practice, not excessive, cash-method taxpayer, etc.). Use the publication’s Figure B flowchart to check.
- Spread ratably over the life of the loan in most other cases, including refinances and second homes.
Seller-paid points can be deductible by the buyer if tests are met. Points are reported on Form 1098 if $600 or more in interest was paid.
How to Calculate Your Deductible Mortgage Interest (Worksheet)?
If your total debt exceeds the limits, use Table 1 (the Qualified Loan Limit Worksheet) in Part II of Publication 936:
- Calculate average balances for grandfathered debt, pre-2018 acquisition debt, and post-2017 acquisition debt.
- Determine your qualified loan limit (the smaller of actual debt or the statutory caps).
- Prorate your total interest paid by the ratio of qualified limit to total average balances.
Two methods are allowed for average balances: first-and-last-day or interest-paid divided by annual interest rate. The publication includes step-by-step instructions and examples.
Figure A in the publication is a helpful flowchart to quickly determine if your interest is fully deductible without the worksheet.
Reporting Mortgage Interest on Your 2025 Tax Return
Report your deduction on Schedule A (Form 1040):
- Line 8a: Interest and points reported on Form 1098
- Line 8b: Other deductible home mortgage interest not on Form 1098
- Line 8c: Points not reported on Form 1098
If you have multiple borrowers, attach a statement showing each person’s share. Excess interest that qualifies for business or rental use goes on the appropriate schedule (C, E, F, etc.).
Common Mistakes to Avoid
- Claiming interest on home equity debt used for non-home purposes
- Forgetting to prorate points on refinances
- Deducting mortgage insurance premiums (now expired)
- Using the wrong debt limit based on loan date
- Failing to itemize when the standard deduction is higher
Always keep Form 1098, loan documents, and records of how home equity funds were spent.
Special Situations Covered in IRS Publication 936
The guide also addresses:
- Interest paid up to the date of sale
- Prepayment penalties and late charges
- Reverse mortgages (interest generally not deductible until paid)
- Ministers and military housing allowances
- Divorced or separated individuals
- Homes destroyed by disaster
- Cooperative housing shares
Frequently Asked Questions About IRS Publication 936
Does Publication 936 apply to my 2025 taxes?
Yes — it is specifically for 2025 returns.
Can I deduct interest on a $900,000 mortgage taken out in 2024?
Only on the first $750,000 (or $1 million if the debt qualifies under pre-2018 rules).
What if I have both an old mortgage and a new one?
Combine the balances and apply the appropriate limits.
Where can I get the latest updates?
Check IRS.gov/Pub936 for future developments.
Conclusion: Use IRS Publication 936 to Save on Taxes in 2025
IRS Publication 936 remains the essential resource for every U.S. homeowner claiming the mortgage interest deduction. By understanding the debt limits, qualified use rules, and worksheet calculations, you can confidently maximize your deduction while avoiding costly mistakes.
Download the full publication today at IRS.gov and consult a tax professional or use IRS Free File if your situation is complex. Proper use of this deduction can significantly lower your tax bill and make homeownership more affordable.
Stay compliant and informed — bookmark IRS.gov/publications/p936 and review it every tax season. For personalized advice, contact a qualified tax advisor or the IRS directly.